1. Field of the Invention
The present invention relates to sectional doors. More specifically, it relates to sectional doors comprising a plurality of insulated panel sections which pivot relative to each other, allowing the door to be moved along a track from a vertical closed position to a rolled up position at the top of the door.
2. Background of the Prior Art
The use of sectional doors is well known. Such doors may be designed for rolling the sections or slats into a so-called "curtain coil" adjacent the top of the door. Such sectional doors are often used for truck unloading docks at warehouses or similar industrial facilities.
Since such sectional doors are generally exposed to rain, snow, wind, and sun, it is generally desirable to make these out of materials which are resistant to wear caused by these elements. Accordingly, steel, aluminum, and similar substances are often used for such sectional doors. However, such weather resistant substances are disadvantageous in that they are good thermal conductors. The high thermal conductivity of such substances has caused the loss of heat from inside the warehouse or similar facility.
In order to counter this loss of heat, various types of insulated slats or door sections have heretofore been made. However, the use of such insulated door sections has often required the complete redesign of the door itself in addition to the track in which it slides. In addition, such insulated door sections often require difficult and/or time consuming techniques for installing the insulation. On the other hand, if the installing of the insulation is made easy by the design, insulation may be lost from the door as by breaking of solid insulation or leakage of fiber insulation.
Prior art insulated door sections or slats have additionally been subject to problems caused by the differing thermal expansion of the outside weather resistant portion (e.g. metal or aluminum) of the door and the insulation. For example, if foamed polystyrene is used as an insulation and is bonded to a steel or metallic front face of a door, a change in temperature will expand the polystyrene and the front portion of the door at differing rates, thereby tending to sever the bond between the polystyrene and the front section.